Foreign text in Blender isn't processed correctly
Interface
The wiki page on Blender Internationalization shows how to set your preferred language

3D


You can enter foreign languages with alternative symbols (like a cyrillic alphabet). You must pick a font that supports the extended character set. The default Bfont does not have many extended characters, that's why you aren't seeing them. You can read more about support for fonts on the Modeling/Text wiki page

3D using the Text Editor